1. Field of the Invention
The present invention relates to plasma process devices, and more specifically, to a plasma process device capable of performing a processing such as deposition, etching and ashing to a large size, rectangular glass substrate using plasma.
2. Description of the Background Art
Conventional plasma process devices to perform deposition, etching and ashing using plasma are known. One of known methods of generating plasma in such a plasma process device is an electron cyclotron resonance plasma excitation method according to which plasma is excited using a microwave and a DC magnetic field. In the electron cyclotron resonance plasma excitation method, however, stable plasma results only if the pressure is set to a level of several mTorr or less at the time of generating plasma. In addition, since the electron temperature in plasma is high, the plasma formed using the electron cyclotron resonance plasma excitation method is not suitable for the process such as deposition as described above. In the electron cyclotron resonance plasma excitation method, a DC magnetic field must be applied, which necessitates the entire device to have a large size. As a result, the manufacturing cost of the plasma process device is disadvantageously high.
Meanwhile, there is a known method of exciting plasma using the surface wave mode of microwave propagating through dielectric rather than using an electron cyclotron resonance method with a DC magnetic field as described above. The plasma excitation method using the surface wave of a microwave can produce stable plasma if the pressure is set in a relatively broad range from several ten mTorr to several Torr or higher. Since the electron temperature in the plasma is relatively low, surface wave excited plasmas are suitable for any of the above processings such as deposition may result.
In a process such as plasma CVD (Chemical Vapor Deposition) and etching, a reaction gas must be introduced uniformly over the entire surface of substrate subject to a reactive process. This is to assure process condition uniformity for deposition, etching or the like over the entire substrate. As one known means for achieving this is the use of a shower plate to supply a reaction gas in a plasma process device. Herein, the shower plate refers to a plate shaped member positioned to oppose a substrate to be processed and having a plurality of reaction gas inlets to introduce a reaction gas into a processing chamber in which the substrate is placed.
As a conventional plasma process device using a method of exciting plasma using the surface wave of a microwave as described above together with a shower plate, a plasma process device using a radial line slot antenna has been known. FIG. 16 is a schematic cross sectional view of a conventional plasma process device using a radial line slot antenna. Referring to FIG. 16, the plasma process device will be described.
Referring to FIG. 16, plasma process device 150 includes a vacuum vessel 156 as a processing chamber, a shower plate 153, a dielectric plate 152, a radial line slot antenna 151 and an exhaust pump 155. In vacuum vessel 156, a circular substrate 154 subjected to deposition process or the like is placed on a substrate holder. Shower plate 153 of dielectric is provided on the upper wall surface of vacuum vessel 156 opposing substrate 154. Dielectric plate 152 is provided above shower plate 153 with a gap 163 therebetween. Radial line slot antenna 151 is provided on dielectric plate 152. Shower plate 153, dielectric plate 152 and radial line slot antenna 151 have a circular shape when viewed from the top. A reaction gas inlet passage 157 is formed to connect the gap 163 between shower plate 153 and dielectric plate 152. A reaction gas introduced to gap 163 from reaction gas inlet passage 157 is let into vacuum vessel 156 through the gas inlets formed in shower plate 153.
Substantially homogeneous plasma 158 is formed over the entire surface of substrate 154 from the reaction gas by the microwave introduced into vacuum vessel 156 from radial line slot antenna 151 through dielectric plate 152, gap 163 and shower plate 153 formed of dielectric. With plasma 158, a processing such as deposition may be performed on the surface of substrate 154. The reaction gas which have not contributed to the processing and the gas generated by the reaction at the substrate surface are let out of vacuum vessel 156 through exhaust pump 155.
FIG. 17 is a perspective cross sectional view of the radial line slot antenna shown in FIG. 16. Referring to FIG. 17, the radial line slot antenna will be described.
Referring to FIG. 17, radial line slot antenna 151 includes a coaxial waveguide 160, a ground plate 159 formed of conductor, a dielectric plate 161 and a slot plate 164 of conductor having slots 162. Dielectric plate 161 is provided under ground plate 159. A slot plate 164 is provided under dielectric plate 161. Coaxial waveguide 160 is connected to dielectric plate 161. A microwave is transmitted to dielectric plate 161 from coaxial waveguide 160. Dielectric plate 161 serves as a radial microwave transmission path. A microwave is radiated through slots 162 formed in slot plate 164 from the entire bottom surface of radial line slot antenna 151.
In the conventional plasma process device using the radial line slot antenna, plasma excitation with a microwave and uniform supply of a reaction gas to the processing chamber using the shower plate are simultaneously performed. The plasma process device using the radial line slot antenna described above suffers from the following problem.
More specifically, referring to FIG. 16, in the conventional plasma process device, a microwave used to form plasma 158 is supplied from radial line slot antenna 151 into vacuum vessel 156 as a processing chamber through dielectric plate 152, gap 163 and shower plate 153. At this time, gap 163 serving as a transmission path for the microwave also function as a supply passage for a reaction gas to vacuum vessel 156. As a result, there is the reaction gas to generate plasma in gap 163. Therefore, the microwave transmitted from radial line slot antenna 151 into vacuum vessel 156 can generate plasma when the gas pressure in gap 163 and the microwave conditions are inappropriate. If plasma is thus generated in gap 163, shower plate 153 and dielectric plate 152 could be damaged by this plasma. In order to prevent the plasma (abnormal plasma) from being generated in gap 163, the pressure of the reaction gas in gap 163 was set significantly higher than the pressure of the reaction gas in vacuum vessel 156. This is for the following reason: electrons in the reaction gas are accelerated by an electric field by the microwave. If however the pressure of the reaction gas in gap 163 is set to a high level of 10 Torr or more, for example, the electrons can collide with other gas atoms or molecules before they are accelerated by the above electric field. As a result, the electrons will no longer have enough energy to generate plasma, so that the plasma can be restrained from being generated in gap 163.
While the pressure of the reaction gas in gap 163 is set to a high level, the pressure inside vacuum vessel 156 must be maintained at a level of several mTorr. As a result, the pressure of the reaction gas in gap 163 is kept at a high level, while the supply of the reaction gas to vacuum vessel 156 must be sufficiently small. Therefore, the easiness for the reaction gas to flow (conductance) through the reaction gas inlets formed in shower plate 153 must be small. In order to realize such small conductance, fine gas inlets in shower plate 153 must be formed with extremely high precision (a precision in the order of 10 xcexcm). Meanwhile, shower plate 153 must be formed using dielectric such as ceramic to allow a microwave to propagate. It is extremely difficult to form gas inlets having such high precision in the dielectric. As a result the manufacturing cost of the shower plate is disadvantageously high.
Since the pressure of the reaction gas in gap 163 must be kept at a high level, process conditions such as the component ratio or flow rate of the reaction gas can be hardly precisely controlled. As a result, the process conditions such as the gas component ratio are shifted from a prescribed numerical range, which makes it difficult to adjust the process conditions, and plasma process such as deposition can no longer performed in a prescribed condition.
In addition, as shown in FIGS. 16 and 17, the conventional radial line slot antenna 151 is circular, in order to apply it to a rectangular substrate for used in a TFT liquid crystal display device or the like, shower plate 153 larger than the rectangular substrate must be used so that the entire surface of the rectangular substrate can be covered. Such rectangular substrates have been increased in size from 500 mmxc3x97500 mm to 1 mxc3x971 m as the liquid crystal display device has come to have a larger size. Radial line slot antenna 151 and shower plate 153 are formed using dielectric such as ceramic as described above. Since it would be difficult to form a large size dielectric plate of ceramic or the like, the conventional plasma process device cannot cope with the large size rectangular type substrate.
The present invention is directed to a solution to the above described problem, and it is an object of the present invention to provide a plasma process device capable of forming homogeneous plasma, and coping with a large area substrate less costly.
A plasma process device according to one aspect of the present invention includes a processing chamber, microwave guiding means, a shower plate, and a reaction gas supply passage. In the processing chamber, a processing using plasma is performed. The microwave guiding means guides a microwave into the processing chamber. The shower plate has a gas inlet hole to supply to the processing chamber a reaction gas attaining a plasma state by the microwave, and a lower surface facing the processing chamber and an upper surface positioned on the opposite side of the lower surface. The reaction gas supply passage is positioned on the upper surface of the shower plate to supply the reaction gas to the gas inlet hole. A wall surface of the reaction gas supply passage includes an upper surface of the shower plate and a conductor wall surface provided opposing the upper surface.
In this case, the microwave is not transmitted through the conductor. As a result, since the wall surface of the gas supply passage positioned on the upper surface of the shower plate includes the conductor wall surface, of the microwave transmitted from the microwave guiding means to the processing chamber, a component having a large electric field amplitude can be prevented from being guided into the reaction gas supply passage. As a result, formation of plasma (abnormal plasma formation) from the reaction gas in the reaction gas supply passage caused by the microwave can be prevented. Therefore, the wall surface of the reaction gas supply passage, in other words, the upper surface of the shower plate or the like can be prevented from being damaged by plasma.
Since abnormal plasma can be prevented from being generated in the reaction gas supply passage, the pressure of the reaction gas in the reaction gas supply passage can be set lower than the conventional device. Thus, the difference between the pressure of the reaction gas in the reaction gas supply passage and the pressure of the reaction gas in the processing chamber can be reduced, so that the conductance of the reaction gas in the gas inlet hole in the shower plate can be larger than the conventional case. Therefore, the size of the gas inlet hole in the shower plate can be set larger than the conventional device, so that high precision machining required by the conventional device in processing the gas inlet holes is no longer necessary. As a result, the manufacturing cost of the shower plate can be reduced.
Since the difference between the pressure of the reaction gas in the reaction gas supply passage and the pressure of the reaction gas in the processing chamber can be reduced, process conditions such as the components of the reaction gas may be more readily adjusted than the conventional device. Thus, plasma of prescribed components may be readily obtained.
In addition, since the shower plate is used to supply the reaction gas uniformly in the processing chamber, homogeneous plasma can be obtained.
A plasma process device according to another aspect of the present invention includes a processing chamber, microwave guiding means, a shower plate, and a reaction gas supply passage. In the processing chamber, a processing using plasma is performed. The microwave guiding means has an opening formed on the processing chamber to guide a microwave into the processing chamber. The shower plate is positioned between the processing chamber and the microwave guiding means and has a gas inlet hole to supply to the processing chamber a reaction gas attaining a plasma state by the microwave. The reaction gas supply passage is formed in a region other than the region under the opening of the microwave guiding means to supply the reaction gas to the gas inlet hole.
In this case, the microwave radiated from the opening of the microwave guiding means is transmitted to the shower plate, and into the processing chamber from the shower plate. Thus, the region positioned under the opening of the microwave guiding means serves as the transmission path of the microwave. The reaction gas supply passage is formed in a region other than the region under the opening of the transmission path of the microwave, so that the reaction gas supply passage and the transmission path of the microwave can be located so as not to overlap one another. Therefore, a component of the microwave having a large electric field amplitude can be surely prevented from being irradiated in the reaction gas supply passage, so that plasma caused by irradiation of the microwave upon the reaction gas can be prevented from being generated in the reaction gas supply passage. As a result, the wall surface of the reaction gas supply passage or the like can be prevented from being damaged by the plasma.
In addition, since abnormal plasma can be prevented from being generated in the reaction gas supply passage, the pressure of the reaction gas in the reaction gas supply passage can be set lower than the conventional device. Thus, the difference between the pressure of the reaction gas in the reaction gas supply passage and the pressure of the reaction gas in the processing chamber can be reduced, so that the conductance of the reaction gas in the gas inlet hole in the shower plate can be larger than the conventional case. Therefore, the size of the gas inlet hole in the shower plate can be set larger than the conventional device, so that high precision machining required by the conventional device is no longer necessary in processing the gas inlet hole. As a result, the manufacturing cost of the shower plate can be reduced.
Since the difference between the pressure of the reaction gas in the reaction gas supply passage and the pressure of the reaction gas in the processing chamber can be reduced, process conditions such as the components of the reaction gas can be adjusted more easily than the conventional device.
The use of the shower plate allows the reaction gas to be uniformly supplied in the processing chamber, so that homogeneous plasma may be obtained.
A plasma process device according to another aspect of the present invention includes a processing chamber, microwave guiding means, a shower plate, and a reaction gas supply passage. In the processing chamber, a processing using plasma is performed. The microwave guiding means guides a microwave into the processing chamber. The shower plate has a gas inlet hole to supply to the processing chamber a reaction gas attaining a plasma state by the microwave. The reaction gas supply passage is positioned on the shower plate and formed in a region other than the transmission path of the microwave guided into the processing chamber by the microwave guiding means for supplying the reaction gas to the gas inlet hole.
Thus, since the reaction gas supply passage is formed in a region other than the transmission path of the microwave, a component of the microwave having a large electric field amplitude can be prevented from being irradiated into the reaction gas supply passage. As a result, abnormal plasma caused by irradiation of the microwave upon the reaction gas can be surely prevented from being generated. Therefore, the inner wall of the reaction gas supply passage can be prevented from being damaged by the abnormal plasma.
Since the abnormal plasma can be prevented from being generated in the gas supply passage, the pressure of the reaction gas in the reaction gas supply passage can be set lower than the conventional level. As a result, the difference between the pressure of the reaction gas in the reaction gas supply passage and the pressure of the reaction gas in the processing chamber can be reduced, and the conductance of the reaction gas in the reaction gas inlet hole in the shower plate can be set larger than the conventional device. As a result, the size of gas inlet hole can be increased compared to the conventional device, and therefore high precision machining required in processing the gas inlet hole by the conventional device is no longer necessary. This allows the manufacturing cost of the shower plate to be reduced.
Since the difference between the pressure of the reaction gas in the reaction gas supply passage and the pressure of the reaction gas in the processing chamber can be reduced, process conditions such as the components of the reaction gas can be adjusted more easily than the conventional device.
Since the reaction gas can be uniformly supplied in the processing chamber using the shower plate, homogeneous plasma can be obtained.
A plasma process device according to another aspect of the present invention includes a processing chamber, microwave guiding means, a shower plate, and a reaction gas supply passage. In the processing chamber, a processing using plasma is performed. The microwave guiding means guides a microwave into the processing chamber. The shower plate has a gas inlet hole to supply to the processing chamber a reaction gas attaining a plasma state by the microwave. The reaction gas supply passage is positioned on the shower plate and isolated from the microwave guiding means by a conductor for supplying the reaction gas to the gas inlet hole.
In this case, since the microwave is not transmitted through the conductor, if the microwave guiding means and the reaction gas supply passage are isolated by the conductor, a component of the microwave from the microwave guiding means having a large electric field amplitude can be surely prevented from being irradiated upon the reaction gas supply passage. As a result, in the reaction gas supply passage, abnormal plasma caused by irradiation of the microwave upon the reaction gas in the reaction gas supply passage can be prevented from being generated. Therefore, the inner wall or the like of the reaction gas supply passage can be prevented from being damaged by this abnormal plasma.
Since abnormal plasma can be prevented from being generated in the reaction gas supply passage, the pressure of the reaction gas in the reaction gas supply passage can be set lower than the conventional device. Thus, the difference between the pressure of the reaction gas in the reaction gas supply passage and the pressure of the reaction gas in the processing chamber can be reduced, so that the conductance of the reaction gas in the gas inlet hole in the shower plate can be larger than the conventional case. Therefore, the size of the gas inlet hole in the shower plate can be set larger than the conventional device, so that high precision machining required by the conventional device in processing the gas inlet hole is no longer necessary. As a result, the manufacturing cost of the shower plate can be reduced.
Since the difference between the pressure of the reaction gas in the reaction gas supply passage and the pressure of the reaction gas in the processing chamber can be reduced, process conditions such as the components of the reaction gas can be adjusted more easily than the conventional device.
The use of the shower plate allows the reaction gas to be uniformly supplied in the processing chamber using the shower plate, so that homogeneous plasma may be obtained.
In a plasma process device according to any of the above aspects or another aspect, the shower plate may have a lower surface facing the processing chamber, and an upper surface positioned on the opposite side of the lower surface, and the wall surface of the reaction gas supply passage may include an upper surface of the shower plate and a conductor wall surface opposing the upper surface.
In this case, since the wall surface of the reaction gas supply passage includes a conductor wall surface of conductor which does not transmit the microwave, a component of the microwave having a large electric field amplitude can be surely prevented from being irradiated from the microwave guiding means to the reaction gas supply passage. As a result, abnormal plasma can be more surely prevented from being generated in the reaction gas supply passage.
In a plasma process device according to any of the above aspects or another aspect of the present invention, the gas inlet hole in the shower plate may be formed penetrating from the upper surface to lower surface of the shower plate, and the gas inlet hole at the lower surface of the shower plate may have a diameter larger than the diameter of the gas inlet hole at the upper surface of the shower plate.
In this case, a cross section of the gas inlet hole may be a shape broader from the upper surface to lower surface of the shower plate. As a result, the reaction gas to be introduced from the gas inlet hole to the processing chamber may be introduced not only in the vertical direction but also in an oblique direction with respect to the lower surface of the shower plate. As a result, the distribution of the reaction gas may be more homogeneous in the processing chamber. As a result, the plasma process can be performed in more uniform conditions.
In a plasma process device according to any of the above aspects or another aspect of the invention, the shower plate may include a plurality of shower plate portions.
In this case, small size shower plate portions may be manufactured using existing manufacturing equipment and combined to form a shower plate having a large area. As a result, a large size shower plate can be readily provided.
Such small size shower plate portions of equal quality can be more readily obtained using existing manufacturing equipment than forming a large size shower plate. As a result, a large shower plate of more equal and good quality may be obtained than forming a large shower plate as an integral form.
In the plasma process device using the shower plate of such a plurality of shower plate portions, if any of shower plate portions is damaged, only the damaged shower plate is replaced, so that the equipment can be readily and quickly repaired. As a result, time and labor required for maintenance of the plasma process device can be reduced.
In a plasma process device according to any of the above aspects or another aspect of the present invention, the isolation distance between a lower surface of the shower plate facing the processing chamber and a conductor wall surface provided opposing an upper surface positioned on the opposite side of the lower surface may be a integral multiple of half a guide wavelength of the microwave (integral multiple of half a wavelength of the microwave in microwave guide means).
Thus, cancellation of microwaves can be prevented, and more homogeneous and efficient plasma excitation can be achieved.
In a plasma process device according to any of the above aspects or another aspect of the present invention, the shower plate may include dielectric.
In this case, the microwave is transmitted through the dielectric, the microwave supplied from the microwave guiding means can be readily transmitted to the processing chamber through the shower plate.
In a plasma process device according to any of the above aspects or another aspect of the present invention, the dielectric is ceramic containing aluminum nitride as a main constituent.
In this case, since aluminum nitride has high thermal conductivity, if the shower plate is locally heated by plasma formed in the processing chamber, the locally applied heat can be quickly diffused to the entire shower plate. As a result, the shower plate can be prevented from being damaged by the local heating.
By using such a material having high thermal conductivity for the shower plate, if a high temperature portion is generated in the processing chamber, the heat of the high temperature portion can be quickly diffused to another region through the shower plate. As a result, the temperature of the processing chamber may be readily equalized.
In a plasma process device according to any of the above aspects or another aspect of the present invention, a vessel member, a pedestal, and a shower plate securing member may be provided. The vessel member may form a processing chamber, and the pedestal may be secured to the vessel member. The shower plate securing member may secure the shower plate by pressing the shower plate to the pedestal.
In this case, if a screw is used for securing the shower plate to the pedestal, a screw hole to receive the screw must be formed in the shower plate of dielectric. The processing using the screw increases the manufacturing cost of the shower plate. In the plasma process device according to the present invention, however, the shower plate is secured to the pedestal by pressing the shower plate to the pedestal, and therefore no screw hole is necessary. As a result, the manufacturing cost of the shower plate may be reduced.
In a plasma process device according to any of the above aspects or another aspect of the present invention, flow rate control means for controlling the flow rate of the reaction gas in the gas inlet hole in the shower plate may be provided.
In this case, the flow rate of the reaction gas supplied to the processing chamber may be adjusted by the flow rate control means, and therefore the plasma process condition in the processing chamber may be readily optimized.
In a plasma process device according to any of the above aspects or another aspect of the present invention, the flow rate control means may include a plug to be inserted into the gas inlet hole in the shower plate.
In this case, the conductance of the reaction gas in the gas inlet hole in the shower plate can be changed by changing the diameter of the plug as the inner diameter of the gas inlet hole is fixed. More specifically, as the gas inlet hole in the shower plate, a hole of a prescribed size is formed. Then, the diameter of the plug is determined to form a gap to serve as a gas passage for the reaction gas between the inner wall of the gas inlet hole and the sidewall of the plug. Thus, the gas inlet hole in the shower plate may be readily machined and at the same time the conductance of the reaction gas in the gas inlet hole in the shower plate may be changed by changing the plug. As a result, the cost of the shower plate may be reduced and processing conditions such as the flow rate of the reaction gas may be readily changed.
In a plasma process device according to any of the above aspects or another aspect of the present invention, the shower plate has a substantially rectangular shape when viewed from the top.
In this case, the plasma process device suitable for processing such as deposition and etching by CVD to a rectangular glass substrate used for a liquid crystal device may be obtained.
In a plasma process device according to any of the above aspects or another aspect of the invention, the microwave guiding means may include a single mode microwave waveguide.
In this case, the microwave can be readily controlled and a stable and homogeneous microwave can be transmitted to the processing chamber.